Investigation of photon statistics and correlations of a dye laser

The probability distribution $p\left(n\right)\mathrm{}$ for the detection of $n$ photons emitted by a single-mode dye laser in a short time at various excitations is measured, together with the distribution of time intervals between pairs of detected photons. The first measurement yields the probability density $\mathcal{p}\mathrm{}\left(I\right)\mathrm{}$ and the moments of the light intensity $I$, and the second one the two-time intensity-correlation function. Measurements are also performed at three different wavelengths. $\mathcal{p}\mathrm{}\left(I\right)\mathrm{}$ is found to have a two-component structure, and the relative intensity fluctuations $\frac{〈{\left(\Delta I\right)}^2〉}{{〈I〉}^2}$ grow, apparently without limit, as the excitation tends to zero, so that no thermal state is reached. A possible explanation in terms of pumping fluctuations is discussed. The correlation function has the form of a sum of three exponential functions, and the amplitudes and decay constants of the three components are derived. The effective decay-time constant exhibits a thirteenth-power-law dependence on frequency of the laser light.